1. Field of the Invention
This invention relates to display systems using symbol generators and particularly to a display system having a direction coded incremental digital stroke generator.
2. Description of the Prior Art
Conventional digital stroke generators for providing symbols such as upon the face of a cathode ray tube, utilize a fixed set of hard wired symbol controls that are generated within a limited set of rigid formats and from which individual symbols are selectable. These generators having hard wired symbol controls may be operated with a substantially small memory when generating simple characters such as letters of the alphabet. However, when generating complicated symbols or pictures such as geographic maps showing coastlines, lakes and mountains, the amount of memory required using the hard wired symbol technique is so excessive as to be impractical. Another problem with a stroke generator using fixed wiring for generating symbols is that it lacks flexibility since only characters that have a limited number of variations may be formed. Other problems of digital stroke generators using hard wired symbol techniques is that the hardward is substantially complex, and the symbol length is fixed for each symbol, and the memory must be static so that new display characters and features cannot be generated in real time.